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This work examined the downstream fetal and placental outcomes of introducing a cocktail of uterine-derived growth factors during bovine embryo culture. Abattoir-derived bovine oocytes were matured and fertilized in vitro. On day 4 post-fertilization, ≥ 8-cell embryos were harvested, pooled and exposed to an embryokine mix, termed EFI, which contained recombinant human epidermal growth factor (10 ng/ml), bovine fibroblast growth factor-2 (10 ng/ml) and human insulin-like growth factor 1 (50 ng/ml) or to a carrier-only control treatment (CON). On day 7, individual, transfer-quality embryos were transferred to recipients. Timed ovulation was completed in mature, non-suckled commercial beef cows. Cows either were artificial inseminated (AI) or received an embryo (ET) on day 7 post-estrus (n = 23-31 cows/treatment over 4 replicate studies). The percentage of grade 1 and 2 morulae and blastocysts was greater (P < 0.05) for EFI-treated embryos than CON. The percentage of pregnant cows diagnosed by transrectal ultrasonography did not differ among the AI and ET groups on days 28, 42 and 56 post-estrus. There also were no differences in the ratio of male to female fetuses determined on day 60 post-estrus by transrectal ultrasonography. On day 21 post-estrus, the relative abundance of three interferon-stimulated gene (ISG) transcripts in peripheral leukocytes were not different based on AI/ET group or the sex of the conceptus. Circulating pregnancy-associated glycoprotein (PAG) concentrations differed (P < 0.05) among days. Also, a difference in PAG concentrations (P < 0.05) were detected between male and female pregnancies in the CON-ET group but not in the AI or EFI-ET groups. Crown-rump length was not affected by AI/ET group on day 42 but were less (P < 0.05) in the CON and EFI-ET groups than the AI group on day 56. These findings implicate EFI supplementation as a means for improving transferable embryo production in a bovine IVP system, but it is not clear if this treatment improves embryo competency after ET., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Two experiments were performed to evaluate the effects of 1) increasing supplementation doses of a 50:50 (as-fed) liquid supplement of molasses and crude glycerol (M:G) on ruminal fermentation parameters and blood urea nitrogen (BUN) in beef steers consuming Tifton 85 bermudagrass ( spp.) hay and 2) different proportions of molasses and crude glycerol in a liquid supplement on in vitro fermentation and gas production kinetics. For Exp. 1, 8 ruminally cannulated, Angus-crossbred steers were used in a duplicated 4 × 4 Latin square design, had ad libitum access to Tifton 85 bermudagrass hay, and were randomly assigned to 1 of 4 treatments: 1) CTRL, no supplementation; 2) SUP1, 0.45 kg/d (as fed) of 50:50 M:G; 3) SUP3, 1.36 kg/d (as fed) of 50:50 M:G; and 4) SUP5, 2.27 kg/d (as fed) of a 50:50 M:G. For Exp. 2 in vitro batch cultures were conducted to test the same treatments from Exp. 1 and effects of different proportions of a M:G mixture (100:0, 75:25, 50:50, 25:75, and 0:100) when added to a hay substrate simulating the proportions of hay and liquid supplement used in SUP5. In Exp. 1, increasing doses of liquid supplement linearly decreased ( < 0.001) concentrations of NH-N, BUN, and acetate molar proportions, whereas propionate ( = 0.002) and butyrate ( < 0.001) molar proportions increased linearly. Treatment × time interactions were observed for ruminal pH ( < 0.001), where the greatest decrease was observed at 3 h postfeeding for animals consuming SUP5 (from 6.82 at 0 h to 6.32 at 3 h). In Exp. 2, decreases in acetate molar proportions ( < 0.001) and increases ( < 0.001) in propionate and butyrate molar proportions were also observed for either increasing doses of a 50:50 mixture or increasing proportions of glycerol in the mixture. Total VFA and in vitro organic matter digestibility were increased linearly ( < 0.001) as doses of a 50:50 mixture increased. Increasing doses of 50:50 M:G to growing beef heifers consuming bermudagrass hay caused a shift in VFA profile toward increases in propionate and decreases in acetate molar proportions. This was also confirmed in vitro, as the proportions of crude glycerol increased in a molasses:crude glycerol mix. Thus, molasses and crude glycerol combined seem to be useful to enhance performance in growing cattle consuming forage-based diets.

Utilization of estrus or ovulation synchronization and fixed-timed artificial insemination (TAI) has facilitated the widespread utilization of artificial insemination (AI) and can greatly impact the economic viability of cow-calf systems by enhancing weaning weights. Implementation of TAI programs by beef producers results in limited frequency of handling cattle and elimination of the need to detect estrus. Continued use of intensive reproductive management tools such as estrus synchronization and AI will result positive changes to calving distribution, pregnancy rates, and subsequent calf value., (Copyright © 2016 Elsevier Inc. All rights reserved.)

The effects of administration of recombinant bovine ST (bST) on plasma hormone concentrations of cows, conceptus development, and postnatal calf performance were examined. Lactating beef cows ( = 190) were exposed to a fixed-time AI (TAI) protocol from d -10 to 0 (TAI on d 0). Cows were blocked by breed and stratified by days postpartum and then randomly assigned to receive, subcutaneously 1) 2 injections of saline (1 mL of 0.9% saline), 1 on d 0 at TAI and a second injection on d 14 (CTRL; = 53); 2) an injection of 325 mg of bST on d 0 and a saline injection on d 14 (bST0; = 48); 3) a saline injection on d 0 and an injection of 325 mg of bST on d 14 (bST14; = 49); or 4) 2 injections of 325 mg of bST, 1 on d 0 and a second injection on d 14 (bST0+14; = 40). Pregnancy status, crown-to-rump length (CRL) on Day 35, and crown-to-nose length (CNL) on Day 65 were determined via transrectal ultrasonography. Blood samples were collected on d 0, 7, 14, 21, 35, and 65, relative to TAI, to determine plasma concentrations of progesterone (P4), IGF-1, and pregnancy-specific protein B (PSPB) and also on d 18 and 21 for isolation of peripheral blood leukocytes for RNA extraction and measurement of interferon-stimulated genes transcript abundance. Individual calf BW was determined at birth and every 30 d until weaning. A subset of 24 calves was randomly selected for liver biopsies at birth to determine mRNA expression of target genes. Administration of bST to cows increased ( < 0.0001) concentrations of plasma IGF-1 for 14 d after injection compared with CTRL but did not affect fetal CRL and CNL ( = 0.23). Cows receiving bST only on d 0 had a greater ( = 0.05) transcript abundance in myxovirus resistance 2 on d 21 compared with 2bST cows (2.0- and 0.8-fold for bST0 and 2bST, respectively), whereas cows receiving bST14 and CTRL were intermediate (1.2- and 0.9-fold, respectively). Calf BW did not differ ( ≥ 0.100) among treatments on d 0, 30, 60, 90, 120, and 150 relative to birth. Injection of bST only on d 0 tended ( = 0.062) to increase calf liver mRNA expression of at birth compared with the calves born to cows in other treatments. Therefore, during a TAI protocol, the administration of 1 or 2 injections of 325 mg of bST to lactating beef cows enhanced their plasma concentrations of IGF-1 but failed to improve fetal size and plasma concentrations of maternal PSPB and P4 and had no effect on postnatal calf growth performance.

Two experiments were conducted to determine the effect of administering PGF at the initiation of the 7-d CO-Synch+controlled internal drug release (CIDR) fixed-timed AI (TAI) protocol on pregnancy rates of suckled beef cows and replacement heifers. Within location, cows were stratified by days postpartum (DPP), BCS, and parity (Exp. 1; = 1,551) and heifers were stratified by BCS (Exp. 2; = 999) and randomly assigned to 1 of 2 treatments: 1) CO-Synch+CIDR (100-μg injection of GnRH at CIDR insertion [d -10] with a 25-mg injection of PGF at CIDR removal [d -3] followed by injection of GnRH and TAI on d 0) or 2) PG-CO-Synch+CIDR (a 25-mg injection of PGF on d -10 of the CO-Synch+CIDR protocol). Follicle diameter and corpus luteum (CL) development were assessed on d -10 and -3, and pregnancy status was determined on d 30 to 35. Blood was collected on d -20, -10, -3, and 0 relative to TAI to determine concentrations of progesterone (P4). In Exp. 1, TAI pregnancy rates did not differ ( = 0.667) between treatments and were affected by BCS ( = 0.003) and DPP ( = 0.006). Concentrations of P4 were greater ( < 0.0001) on d -3 for CO-Synch+CIDR than for PG-CO-Synch+CIDR (4.1 ± 0.2 and 3.4 ± 0.2 ng/mL, respectively). Follicle diameter on d -3 differed ( = 0.05) between PG-CO-Synch+CIDR (13.4 ± 0.3 mm) and CO-Synch+CIDR (12.5 ± 0.3 mm) treatments. Cows with P4 > 2.5 ng/mL on d -10 had greater ( = 0.024) pregnancy rate to TAI (56.5%) compared with cows with 2.5 ng/mL < P4 > 1 (43.0%), whereas cows with P4 < 1 ng/mL were intermediate (51.6%). Cows with a CL on d -10 had greater ( = 0.012) pregnancy rates to TAI than cows without a CL (66.3 vs. 39.4%, respectively). In Exp. 2, TAI pregnancy rates did not differ ( = 0.316) between treatments. Concentrations of P4 differed ( < 0.0001) on d -3 with greater concentrations of P4 for CO-Synch+CIDR than for PG-CO-Synch+CIDR (3.75 ± 0.20 ng/mL and 3.60 ± 0.21 ng/mL, respectively). Follicle diameter was similar ( = 0.749) between treatments on d -10 and -3. Regardless of treatment, cyclic status tended ( = 0.062) to improve pregnancy rates to TAI (55 vs. 45%, for cycling and noncycling heifers, respectively). We concluded that addition of PGF to the 7-d CO-Synch+CIDR protocol decreased concentrations of P4 in cows and heifers and increased follicle diameter at CIDR removal in cows but failed to increase TAI pregnancy rates.

Chitosan was evaluated as a feed additive to mitigate in vivo CH4 emissions in beef cattle. Twenty-four crossbred heifers (BW = 318 ± 35 kg) were used in a randomized block design replicated in 2 periods. The design included a 2 × 3 factorial arrangement of treatments, which included diet (high concentrate [HC] or low concentrate [LC]) and 0.0, 0.5, or 1.0% of chitosan inclusion (DM basis). Diets were offered ad libitum and individual intake was recorded. An in vitro experiment to analyze chitosan’s effect on fermentation parameters and gas production kinetics was performed. A diet effect (P < 0.01) was observed for CH4 emissions expressed as grams/day, grams/kilogram of BW0.75, and grams/kilogram of DMI. Heifers consuming the LC diet produced 130 g of CH4/d vs. 45 g of CH4/d in those consuming the HC diet. Incubation fluid pH increased linearly (P < 0.05) when chitosan was included in HC substrates. In vitro CH4 production was not affected (P > 0.10) by chitosan in HC substrate; however, when incubated with the LC substrate, CH4 production increased quadratically (P < 0.01) as chitosan inclusion increased. A digestibility marker × diet interaction occurred (P < 0.05) for DM, OM, CP, NDF, and ADF digestibility. Diet × chitosan interactions (P < 0.05) occurred for DM, OM, NDF, and ADF digestibility when Cr2O3 was used. When TiO2 was used, diet × chitosan interactions (P < 0.05) were observed for NDF and ADF. However, using indigestible NDF as an internal marker, DM and OM digestibility were improved (P < 0.05) by 21 and 19%, respectively, when chitosan was included in LC diets. In conclusion, feeding up to 1% of chitosan (DM basis) to heifers consuming a LC diet increased apparent total tract digestibility of nutrients. Enteric CH4 emissions were not affected by chitosan feeding, regardless of type of diet, and heifers consuming a 36% concentrate diet produced 2.6 times more methane per day than those consuming an 85% concentrate diet.

Two experiments were performed to evaluate the effects of different levels of supplementation with a 50:50 (as-fed) mixture of molasses:crude glycerol on animal performance, total tract digestibility of nutrients, and ruminal in situ degradability of nutrients in beef heifers and steers consuming Tifton 85 Bermuda grass (Cynodon spp.) hay. For Exp. 1, 24 Angus crossbred heifers (380 ± 31 kg BW) were used in a generalized randomized block design. For Exp. 2, 8 ruminally cannulated Angus crossbred steers (323 ± 42 kg BW) were used in a 4 × 4 duplicated Latin square design. For both experiments, animals were housed in individual pens at the University of Florida Feed Efficiency Facility, had ad libitum access to Tifton 85 Bermuda grass hay, and were randomly assigned to 1 of 4 treatments: 1) CTRL, no supplementation; 2) SUP1, 0.45 kg/d (as fed) of 50:50 mixture; 3) SUP3, 1.36 kg/d (as fed) of 50:50 mixture; and 4) SUP5, 2.27 kg/d (as fed) of a 50:50 mixture. Individual feed intake was recorded. Total DMI increased linearly (P = 0.005) as the level of supplementation increased. Hay intake ranged from 1.36 (CTRL) to 1.23% (SUP5) of BW, and was not affected (P ≥ 0.10) by liquid supplementation. Final BW was not affected by liquid supplementation ( ≥ 0.10). There was a linear increase (P = 0.027) in ADG as the liquid supplementation amounts increased. Liquid supplementation did not affect G:F (P ≥ 0.10). Apparent total tract digestibility of DM, OM, NDF, and ADF increased linearly (P < 0.001), while CP total tract digestibility decreased linearly (P = 0.002) as the level of supplementation increased. Ruminal pH was decreased linearly (P = 0.012) as the level of supplementation increased. No effect (P ≥ 0.10) of liquid supplementation was detected on lag time for NDF and ADF content of bermudagrass hay; however, rate of degradation (Kd) of NDF tended (P = 0.076) to be affected cubically by liquid supplementation. In addition, liquid supplementation linearly decreased (P < 0.05) ED of OM, CP, NDF, and ADF. In conclusion, supplementing up to 2.27 kg/d of a 50:50 mixture of molasses:crude glycerol may stimulate microbial growth and fermentative activity, thereby increasing nutrient digestibility. Increased fiber digestion, along with energy supplementation, led to increased ADG in heifers consuming Bermuda grass hay.

To determine whether supplementation of anti-phospholipase A antibody (aPLA) would alter voluntary DMI, feed efficiency (FE), acute-phase protein concentration, and blood differentials (BD) due to a change in diet from a forage-based to a grain-based diet, individual daily DMI was measured on 80 cross-bred steers during a 141-d period. On d 0, steers were blocked by BW and randomly assigned to receive a growing forage diet containing 1) no additive (CON; = 20), 2) inclusion of 30 mg of monensin and 8.8 mg of tylosin per kg of diet DM (MT; = 20), 3) inclusion of an aPLA supplement at 0.4% of the diet DM (0.4% aPLA; = 20), and 4) inclusion of an aPLA supplement at 0.2% of the diet DM (0.2% aPLA; = 20). On d 60, steers were transitioned into a grain-based diet (90% concentrate) over a 21-d "step-up" period while continuing to receive their supplement treatments and were maintained on the high-grain diet until the end of the trial on d 141. On d 0, 60, 81, and 141, individual shrunk BW was recorded. Blood samples were collected on d 60, 63, 65, 67, 70, 72, 74, 77, 79, 81, and 84 for determination of concentration of plasma ceruloplasmin, haptoglobin, and BD. During the growing forage-diet period, steers from the 0.2% aPLA and 0.4% aPLA treatments had lower ( < 0.05) residual feed intake (RFI; -0.12 ± 0.13 and -0.22 ± 0.13 kg/d, respectively) than steers from the CON treatment (0.31 ± 0.13 kg/d). During the grain-based diet period, the 0.2% aPLA (-0.12 ± 0.10 kg/d), 0.4% aPLA (0.36 ± 0.10 kg/d), and MT (0.10 ± 0.10 kg/d) steers had greater ( = 0.04) RFI than CON steers (-0.37 ± 0.10 kg/d). During the transition phase, white blood cell counts were greater ( = 0.04) for the 0.2% aPLA treatment (13.61 × 10 ± 0.42 × 10 cells/μL) than the 0.4% aPLA and MT treatments (12.16 × 10 ± 0.42 × 10 and 12.37 × 10 ± 0.42 × 10 cells/μL, respectively) and concentrations of lymphocytes also were greater ( = 0.01) for the 0.2% aPLA treatment (7.66 × 10 ± 0.28 × 10 cells/μL) than the 0.4% aPLA and MT treatments (6.71 × 10 ± 0.28 × 10 and 6.70 × 10 ± 0.28 × 10 cells/μL, respectively). Concentrations of plasma ceruloplasmin and haptoglobin were reduced ( < 0.05) for CON compared to aPLA steers (22.2 ± 0.83 vs. 24.4 ± 0.83 mg/dL and 0.18 ± 0.05 vs. 0.26 ± 0.05 mg/mL, respectively). Supplementation of aPLA improved FE of steers fed a forage-based growing diet but not when feeding grain-based diets. The 0.4% aPLA and MT treatments had decreased white blood cell counts and concentration of lymphocytes during the transition period compared to the 0.2% aPLA treatment, and CON steers had reduced concentrations of plasma ceruloplasmin and haptoglobin during the diet transition phase.

In Exp. 1, individual performance and daily DMI was measured on 70 crossbred weaned calves during a 70-d period using a GrowSafe system (GrowSafe Systems Ltd., Airdrie, AB, Canada) at the University of Florida North Florida Research and Education Center Feed Efficiency Facility (FEF). Calves were fed a low-concentrate (LC) growing diet, blocked by weight and sex, and then randomly assigned to pens to receive either no additional supplement (CON; n = 35) or receive a supplement of anti-phospholipase A2 antibody (aPLA2) at an inclusion rate of 0.6% of the diet DM (n = 35). After the 70-d feed efficiency (FE) trial (Phase 1), calves were loaded into a commercial livestock trailer and were driven for approximately 1,600 km during 24 h. Upon return to the FEF (Phase 2), calves were relocated to the same pens and groups and received the same diets and treatments for 28 d. Blood samples from each calf were collected on d 0, 1, 3, 5, 7, 14, 21, and 28 relative to initiation of transportation and were analyzed for determination of concentrations of plasma ceruloplasmin and haptoglobin. In Phase 1, initial BW (242.0 ± 3.7 kg; P = 0.92), BW at d 70 (313.0 ± 4.1 kg; P = 0.79), and ADG (1.01 ± 0.02 kg; P = 0.95) were similar between treatments. However, daily DMI was greater (P = 0.01) for CON (9.18 ± 0.15 kg) than aPLA2 (8.53 ± 0.15 kg). In addition, residual feed intake was greater (P = 0.002) for CON (0.389 ± 0.110 kg/d) than aPLA2 calves (-0.272 ± 0.110 kg/d). In Phase 2, after transportation, there were no differences between treatments on BW loss due to transportation shrink (26.0 ± 0.6 kg; P = 0.86), BW at d 28 (339.0 ± 4.1 kg; P = 0.72), ADG (1.28 ± 0.03 kg/d; P = 0.72), G:F (0.164 ± 0.004; P = 0.83), and concentrations of plasma haptoglobin (0.08 ± 0.02 mg/mL; P = 0.41). However, concentrations of plasma ceruloplasmin were greater (P < 0.001) for CON calves (14.3 ± 0.3 mg/dL) compared to aPLA2 calves (13.0 ± 0.3 mg/dL). In Exp. 2, the effects of aPLA2 inclusion on LC and high-concentrate (HC) substrates on in vitro fermentation parameters were assessed. Addition of aPLA2 had no effects on in vitro fermentation parameters of LC and HC substrates. In conclusion, supplementation of aPLA2 improved FE of growing beef calves when fed LC diets in Phase 1 and addition of aPLA2 had no effect on fermentation parameters of LC and HC substrates. In addition, calves supplemented with aPLA2 had reduced concentrations of plasma ceruloplasmin after 24 h of transportation.

Brahman × British crossbred steers (n = 40 and 38 in yr 1 and 2, respectively) were used to evaluate the effects of calf management systems following early weaning (EW) on growth performance, muscle gene expression, and carcass characteristics. On the day of EW (d 0), steers were stratified by BW and age (95 ± 14 kg; 74 ± 14 d) and randomly assigned to a control treatment that was normally weaned (NW) on d 180 (n = 10 steers/yr) or to 1 of 3 EW treatments: 1) EW and limit fed a high-concentrate diet at 3.5% of BW (as-fed basis) in drylot until d 180 (EW180; n = 10 steers/yr), 2) EW and limit fed a high-concentrate diet at 3.5% of BW (as-fed basis) in drylot until d 90 and then grazed on bahiagrass pastures until d 180 (EW90; n = 10 steers/yr), or 3) EW and grazed on annual ryegrass pastures until d 60 (yr 1; n = 10 steers) or 90 (yr 2; n = 8 steers) and then on bahiagrass pastures until d 180 (EWRG). Early-weaned steers on ryegrass and bahiagrass pastures were supplemented with high-concentrate diet at 1.0% of BW (as-fed basis) until d 180. From d 180 to 270 (yr 1), all EW steers remained in their respective treatments, whereas NW steers were provided high-concentrate diet at 1.0% of BW (as-fed basis) on bahiagrass pastures. In yr 1, feedlot finishing period began on d 270. In yr 2, the study was terminated on d 180. In both years, EW180 steers were heaviest (P < 0.0001) on d 180. On d 180 of yr 1, EWRG steers were lightest (P < 0.0001) and EW90 steers were heavier (P = 0.05) than NW steers, whereas EW90, EWRG, and NW steers had similar BW on d 180 of yr 2 (P ≥ 0.14). On d 90, muscle PPARγ mRNA expression tended (P = 0.07) to be greater for EW180 steers and was greater (P = 0.008) for EW90 vs. EWRG steers but similar (P = 0.25) between EW180 and NW steers. On d 180, PPARγ mRNA was greater (P ≤ 0.06) for EW180 vs. NW, EW90, and EWRG steers. From d 274 to 302, EW180 steers had the least ADG (P ≤ 0.09), whereas EW90 steers had similar (P = 0.19) ADG compared with EWRG steers but greater (P = 0.03) ADG than NW steers. At slaughter, carcass characteristics did not differ (P ≥ 0.22) among treatments. In summary, EW steers provided a high-concentrate diet in drylot for at least 90 d were heavier at the time of normal weaning than NW steers and EW steers grazed on ryegrass pastures for 60 to 90 d and supplemented with concentrate at 1.0% of BW. Feeding a high-concentrate diet immediately after EW enhanced the muscle PPARγ expression but did not enhance marbling at slaughter.

Brahman × British crossbred heifers (n = 40 and 38 heifers in yr 1 and 2, respectively) were used to evaluate the effects of calf weaning age and subsequent management system on growth and reproductive performance. On d 0, heifers were ranked by BW (89 ± 16 kg) and age (72 ± 13 d) and randomly assigned to a conventional management group that was normally weaned on d 180 (NW; n = 10 heifers annually) or early weaned (EW) on d 0 and 1) limit fed a high-concentrate diet at 3.5% of BW (as fed) in drylot until d 180 (EW180; n = 10 heifers annually), 2) limit fed a high-concentrate diet at 3.5% of BW (as fed) in drylot until d 90, then grazed on Bahiagrass pastures until d 180 (EW90; n = 10 heifers annually), or 3) grazed on annual ryegrass pastures until d 60 (yr 1; n = 10 heifers) or 90 (yr 2; n = 8 heifers), then on Bahiagrass pastures until d 180 (EWRG). On d 180, all heifers were grouped by treatment and rotated on Bahiagrass pastures until d 390. Grazing heifers were supplemented at 1.0% BW until d 180 and at 1.5% BW from d 180 to 390. From d 0 to 90, EW180 and EW90 heifers were heavier (P ≤ 0.02) than NW and EWRG heifers, whereas NW heifers tended (P = 0.09) to be heavier on d 90 than EWRG heifers. In yr 1 and 2, EW180 heifers were heaviest (P < 0.0001) on d 180. In yr 1, EWRG heifers were lightest (P < 0.0001), whereas EW90 and NW heifers had similar BW (P = 0.58). Conversely, EW90, EWRG, and NW heifers achieved similar BW on d 180 of yr 2 (P ≥ 0.18). Positive correlations were detected (P ≤ 0.05) between liver IGF-1 mRNA abundance on d 90 and ADG from d 0 to 90 and between liver IGF-1 mRNA abundance on d 180 and ADG from d 90 to 180. The EW180 heifers were youngest (P ≤ 0.01) at puberty. From d 260 to 340, the percentage of pubertal heifers was greater (P ≤ 0.03) for EW90 vs. NW heifers but did not differ (P ≥ 0.15) between EWRG and NW heifers. The ADG from d 0 to 90 and the plasma IGF-1 on d 90 and 180 explained approximately 34% of the variability in age at puberty. In summary, the EW90 and EW180 heifer management systems evaluated in this study altered the BW at the time of NW and were good alternatives for anticipating puberty achievement compared to NW heifers.

We hypothesized that pregnancy outcomes may be improved by inducing luteal regression, ovulation, or both (i.e., altering progesterone status) before initiating a timed-artificial insemination (TAI) program in suckled beef cows. This hypothesis was tested in two experiments in which cows were treated with either PGF2α (PG) or PG + GnRH before initiating a TAI program to increase the proportion of cows starting the program in a theoretical marginal (<1 ng/mL; experiment 1) or elevated (≥1 ng/mL; experiment 2) progesterone environment, respectively. The control was a standard CO-Synch + controlled internal drug release (CIDR) program employed in suckled beef cows (100 μg GnRH intramuscularly [IM] [GnRH-1] and insertion of a progesterone-impregnated intravaginal CIDR insert on study Day -10, 25 mg PG and CIDR insert removal on study Day -3, and 100 μg GnRH IM [GnRH-2] and TAI on study Day 0). In both experiments, blood was collected before each injection for later progesterone analyses. In experiment 1, cows at nine locations (n = 1537) were assigned to either: (1) control or (2) PrePG (same as control with a PG injection on study Day -13). The PrePG cows had larger (P < 0.05) follicles on study Day -10 and more (P < 0.05) ovulated after GnRH-1 compared with control cows (60.6% vs. 36.5%), but pregnancy per TAI was not altered (55.5% vs. 52.2%, respectively). In experiment 2, cows (n = 803) at four locations were assigned to: (1) control or (2) PrePGG (same as control with PG injection on study Day -20 and GnRH injection on study Day -17). Although pregnancy per TAI did not differ between control and PrePGG cows (44.0% vs. 44.4%, respectively), cows with body condition score greater than 5.0 or 77 or more days postpartum at TAI were more (P < 0.05) likely to become pregnant than thinner cows or those with fewer days postpartum. Presynchronized cows in both experiments were more (P < 0.05) likely than controls to have luteolysis after initial PG injections and reduced (P < 0.05) serum progesterone; moreover, treatments altered the proportion of cows and pregnancy per TAI of cows in various progesterone categories before the onset of the TAI protocol. In combined data from both experiments, cows classified as anestrous before the study but with elevated progesterone on Day -10 had increased (P < 0.05) pregnancy outcomes compared with anestrous cows with low progesterone concentrations. Progesterone concentration had no effect on pregnancy outcome of cycling cows. In summary, luteal regression and ovulation were enhanced and progesterone concentrations were altered by presynchronization treatments before the 7-day CO-Synch + CIDR program, but pregnancy per TAI was not improved., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Eighty-one prepubertal beef heifers were used to evaluate effects of used controlled internal drug release (CIDR) insert heating methods on concentrations of progesterone after CIDR insert reinsertion. Heifers were stratified by weight and birth date and then assigned to receive a new CIDR insert (New; n = 10) or 1 of 8 used (7 d prior use) CIDR insert treatments: 1) no processing (Used; n = 10), 2) autoclaved (Autoclaved; n = 8), 3) processed in dishwasher (Dishwasher; n = 8), 4) processed in microwave for 30 s (Microwave; n = 10), 5) processed in toaster oven (Oven; n = 9), 6) processed in clothes dryer (Dryer; n = 10), 7) processed in boiling water (Boiled; n = 8), or 8) stored outdoors for 60 d (Outside; n = 8). Used CIDR inserts were processed at 121°C for 30 min for autoclaved and oven treatments, at 121°C for boiled treatment, and for 30 min for dryer and dishwasher treatments. Blood samples were collected on d -10, immediately before CIDR insert insertion (d 0), 3 h after CIDR insert insertion (3 h), daily while CIDR insert was in place (d 1 to 11), and 24 h after CIDR insert removal (d 12) for analysis of concentrations of progesterone. Subjective color scores (1 = bright white to 5 = completely stained yellow/red) were assigned to each CIDR insert after d 11. A treatment × time interaction (P < 0.0001) was present for concentrations of progesterone. Concentrations of progesterone were similar (P > 0.10) for heifers receiving a used CIDR insert compared with heifers receiving CIDR inserts processed in a dishwasher, microwave, oven, dryer, or boiling water (collectively reported as "Processed"). However, heifers receiving autoclaved CIDR inserts had greater (P < 0.05) concentrations of progesterone from h 3 to d 3 but similar (P > 0.10) concentrations of progesterone from d 4 to d 11 compared with heifers receiving used or processed CIDR inserts. From d 1 to 11 heifers receiving outside CIDR inserts had decreased (P < 0.05) concentrations of progesterone compared with all other treatments. Heifers receiving autoclaved CIDR inserts had greater (P < 0.05) concentrations of progesterone compared with all other treatments at 3 h and 1 d, whereas heifers receiving new CIDR inserts had greater (P < 0.05) concentrations of progesterone from d 6 to 11 compared with all other treatments. Outside CIDR inserts were more discolored (P < 0.001) compared with all other treatments. Processing used CIDR inserts with a dishwasher, microwave, oven, clothes dryer, boiling water, or full environmental exposure did not result in a pattern of concentrations of progesterone similar to that of autoclaved or new CIDR inserts.

Inclusion of Bos indicus genetics improves production traits of cattle maintained in hot climates. Limited information exists detailing pregnancy-specific events as influenced by variable amounts of Bos indicus genetics. Three experiments were completed to examine the effect of Bos taurus and Bos indicus genotypes on fetal size and plasma pregnancy-associated glycoprotein (PAG) concentrations. In all experiments, cows were bred by AI after synchronization of ovulation. Fetal measurements were completed by transrectal ultrasonography and plasma PAG concentrations were quantified from plasma harvested the day of each fetal measurement. In Exp. 1, fetal size and plasma PAG concentrations were measured at d 53 of pregnancy in cows composed of various fractions of Angus and Brahman (n = 9 to 21 cows/group). Fetus size was greater in cows containing >80% Angus genetics compared with cows containing <80% Angus influence (3.40 ± 0.28 vs. 2.86 ± 0.28 cm crown-rump length; P < 0.01). Plasma PAG concentrations were reduced (P < 0.01) in cows containing >80% Angus genetics when compared with their contemporaries (6.0 ± 1.5 ng/mL vs. 9.4 ± 1.5 ng/mL). In Exp. 2, fetal measurements and plasma PAG concentrations were determined at d 35 and 62 of pregnancy in Angus and Brangus cows. Breed did not affect fetus size at d 35, but Angus cows contained larger fetuses than Brangus cows at d 62 [3.0 ± 0.03 vs. 2.8 ± 0.03 cm crown-nose length (CNL; P > 0.01)]. Plasma PAG concentrations were not different between breed at d 35 and 62 (P > 0.1). In Exp. 3, fetal measurements and plasma samples were collected at d 33/34, 40/41, 47/48, and 54/55 post-AI in Angus and Brangus cows. Fetus size was not different (P > 0.05) between genotypes on d 33/34, 40/41, and 47/48. Angus fetuses were larger than Brangus fetuses at d 54/55 (2.1 ± 0.03 vs. 1.9 ± 0.03 cm CNL; P = 0.001). Plasma PAG concentrations were less in Angus than Brangus cows at each time point (average 4.9 ± 0.9 vs. 8.2 ± 0.9 ng/mL; P = 0.005). In conclusion, these studies determined that the Bos taurus × Bos indicus genotype impacts fetal size and rate of fetal development by 7 wk of gestation. Plasma PAG concentrations were increased in cattle with Bos indicus genetics in 2 of 3 studies, suggesting that genotype is one of several determinants of PAG production and secretion in cattle.

Seventy-four beef heifers were used to evaluate relationships among performance, residual feed intake (RFI), and temperament measured as growing heifers (Phase 1) and subsequently as 3-yr-old lactating beef cows (Phase 2) in the same cohort. In both phases, females were housed in a covered facility and fed similar forage-based diets, and individual feed intakes, BW, BCS, chute scores (CS), exit velocities (EV), and pen scores (PS) were collected throughout the 70-d feeding trials. In Phase 2, cows were milked on trial d 14 (lactation d 28 ± 3.5) and trial d 70 (lactation d 84 ± 3.5) to determine energy-corrected milk (ECM) production. Ultrasonic backfat thickness (BF), and ribeye area (REA) were evaluated on d 0 and 70 of the trial in Phase 2. Heifers were ranked by RFI and placed into Low (<0.5 SD mean RFI; n = 27), Medium (within ± 0.5 SD; n = 23), and High (>0.5 SD mean RFI; n = 24) RFI groups. Body weight, BCS, and ADG were similar among all RFI groups; however, daily DMI differed for all groups (P < 0.01) and was greater (10.76 ± 0.24 kg/d) for High, intermediate (9.88 ± 0.25 kg/d) for Medium, and less (8.52 ± 0.23 kg/d) for Low RFI heifers. When cow performance was analyzed based on RFI rank as heifers, BW, BCS, ADG, RFI, d 14 and d 70 ECM, BF, and REA were similar among RFI groups; however, cows that were most efficient as heifers (Low) had decreased (P < 0.05) daily DMI values (10.30 ± 0.41 kg/d) compared with cows that ranked Medium (11.60 ± 0.44 kg/d) or High (11.50 ± 0.43 kg/d) as heifers. The Pearson rank correlation between Phase 1 and 2 RFI was r = 0.13 (P = 0.30), and Pearson rank correlations showed no relationship (P > 0.1) between RFI and temperament. Phase 1 CS was negatively associated with ADG in Phase 1 (r = -0.28; P = 0.02) and 2 (r = -0.32; P = 0.01), and positively associated with d 14 (r = 0.24; P = 0.04) and 70 (r = 0.25; P = 0.03) ECM. Phase 2 CS was negatively associated with Phase 2 ADG (r = -0.29; P = 0.01) and positively associated with d 14 (r = 0.46; P = 0.001) and 70 (r = 0.33; P = 0.004) ECM. Phase 2 PS also tended to be negatively associated with DMI in Phase 1 (r = -0.20; P = 0.096) and 2 (r = -0.20; P = 0.08). In this study, heifers that were most feed efficient subsequently consumed less feed as lactating cows and maintained similar performance. Feed efficiency was not associated with differences in temperament; however, more excitable females had poorer BW gains and tended to have reduced feed intakes but produced more ECM.

Two experiments were conducted to determine the effect of calf removal (CR) on pregnancy rate (PR) and calf performance in suckled beef cows. Cows in both experiments were synchronized with the 7-d CO-Synch + CIDR protocol [i.e., 100-µg injection of GnRH at controlled internal drug release (CIDR) device insertion (d -7) with 25-mg injection of PGF2α at CIDR removal (d 0), followed by injection of GnRH and timed AI (TAI) on d 3]. Cows were blocked by location (6 locations), stratified by days postpartum (DPP) and parity, and assigned to 1 of 2 treatments in Exp. 1: 1) control (Control; n = 156); 2) calves were separated from their dams between d 0 and 3 (CR72; n = 168); and 1 of 4 treatments in Exp. 2: 1) Control (n = 103); 2) CR72 (n = 104); 3) calves were separated from their dams between d 0 and 2 (CR48A; n = 95); and 4) similar to CR48A but CR between d 1 and 3 (CR48B; n = 53). Transrectal ultrasonography of ovarian structures was performed on d 0, 1, 2, 3, 4, and 10 (in a subset of cows) to determine pregnancy status on d 33. Blood samples were collected on d -14, -7, 0, 3, and 10 (in a subset of cows) to determine concentrations of progesterone (P4) and estradiol (E2). Calves were blocked by age as young (25 to 59 d), medium (60 to 79 d), and old (≥80 d), and were weighed on d 0, 3, 33, and 63. Overall PR did not differ among treatments and averaged 50%. Follicle growth rate from d 0 to 3 tended (P = 0.06) to be greater for CR72 (0.42 ± 0.15 mm/d) compared with Control (0.02 ± 0.15 mm/d). Young (-3.9 ± 0.3%) and old (-3.1 ± 0.4%) calves lost a greater (P < 0.001) percent of BW (PBW) during CR than medium-age (-1.6 ± 0.3%) calves exposed to CR72. In Exp. 2, PR were similar among all 3 locations (49%; P = 0.15). Young (-4.8 ± 0.6%) and medium (-3.0 ± 0.5%) calves lost greater (P < 0.01) percent body weight (PBW) during CR than old (-1.4 ± 0.6%) calves within the CR72 treatment. Calves exposed to CR48 (-2.2 ± 0.6%, -1.1 ± 0.6%, and -2.4 ± 0.6% PBW change for young, medium, and old, respectively) lost more BW than calves in the Control group (-3.7 ± 0.4%, -1.7 ± 0.5%, and -2.1 ± 0.5% PBW change for young, medium, and old, respectively). Subsequent calf weights on d 33 and 63 were greater (P < 0.05) in Controls than cows exposed to CR48 or CR72 treatments. We conclude that CR stimulated follicle growth but failed to enhance PR to TAI. However, CR had a negative impact on subsequent calf performance, which differed, depending on the duration and age of the calf when exposed to CR.

Two experiments were conducted to evaluate the effects of eCG, temporary 72-h calf removal (CR), or both on dominant follicle (DF) diameter and pregnancy rates (PR) in suckled beef cows. For Exp. 1, we hypothesized that CR, eCG, or both at PGF2α administration concomitant with synchronization of ovulation protocol would increase DF diameter and alter patterns of LH, estradiol (E), and progesterone (P4) secretion. Thirty-five multiparous, suckled crossbred beef cows were assigned randomly to a 2 × 2 factorial arrangement of 4 treatments: 1) cows received 100 μg GnRH and a controlled internal drug release (CIDR) insert containing 1.38 g of P4 (d -7) followed in 7 d by 25 mg PGF(2α) and CIDR removal (d 0) followed in 72 h by GnRH and fixed-time AI (d 3; Control; n = 9); 2) similar to control, but calves were removed from their dams for 72 h between d 0 and 3 (COCR; n = 9); 3) similar to control, but cows received 400 IU eCG on d 0 (COeCG; n = 9); and 4) similar to COCR, but cows received 400 IU eCG on d 0 (eCGCR; n = 8). Blood sample collection and ovary scans were performed on d -14, -7, 0, 1, 2, 3, 4, and 10. Pregnancy rate, ovulation response by d 4, and peak concentrations of LH before 72 h after PGF(2α) were greater (P < 0.05) for cows exposed to CR (COCR and eCGCR) than for cows not exposed to CR (Control and COeCG). Follicle diameter on d 3 was greater (P = 0.02) for cows receiving eCG (COeCG and COeCG; 14.9 ± 0.5 mm) than for cows receiving no eCG (Control and COCR; 13.1 ± 0.5 mm). Concentrations of E were greater (P < 0.05) at 32 h for COCR (8.2 ± 1.0 pg/mL) and eCGCR (8.5 ± 0.9 pg/mL) than in Control (4.9 ± 1.2 pg/mL) and COeCG (4.6 ± 1.1 pg/mL) and at 44 h after PGF(2α) for eCGCR (11.7 ± 1.6 pg/mL) compared with Control (6.9 ± 1.7 pg/mL), COCR (7.1 ± 1.5 pg/mL), and COeCG (7.5 ± 1.7 pg/mL). In Exp. 2, we determined whether administration of 200 IU eCG improved PR in suckled beef cows. The Control (n = 261) and COeCG (n = 252) treatments were similar to those previously described in Exp. 1; however, the interval from PGF(2α) to fixed-time AI was 66 h and 200 IU of eCG were administered to the COeCG group. Pregnancy rates did not differ (P > 0.10) between COeCG (43%) and Control (50%). We conclude that eCG increased DF diameter and CR resulted in a greater percentage of cows experiencing LH peak before 72 h after PGF(2α) and ovulation response; however, eCG failed to improve PR to timed AI.